BMW Motorrad says 'Big Boxer' is its most powerful boxer engine ever

BMW is dishing new details on the newly developed but throwback-style 2-cylinder boxer engine that features in four Motorrad concept bikes unveiled over the past year that look increasingly likely to presage production motorcycles.

Dubbed the “Big Boxer” by BMW, the 1,802 cc (1.8-liter) flat-twin features in the Concept R18/2, shown earlier this month at EICMA, the Concept R18, and the Motorrad-suppported concepts the Departed by ZON and Revival Cycles’ Birdcage. It’s said to be the most powerful BMW boxer engine, making 91 horsepower and 116 pound-feet of torque and is said to balance high pulling power and running smoothness.

BMW says the engine harkens to the first air-cooled Motorrad boxer engines that debuted in 1923 and stayed in production for about 70 years, with the same overhead valve drive and separate engine and transmission housings and built to be reliable and easy to maintain. but the new Big Boxer is air- and oil-cooled, of course, and the quenched- and tempered-steel crankshaft has an additional main bearing at the center to prevent against unwanted bending vibrations in the large-volume cylinders. It also has a vertically split aluminum engine housing. A wet sump lubrication system supplies the lubricating and cooling oil via a two-stage oil pump and a sleeve-type chain driven by the crankshaft.